1. Field of the Invention
The present invention relates to optical communication by routing optical packets using multiple wavelength labels. More particularly, the present invention relates to a method for routing optical packets using multiple wavelength labels that is based on wavelength division multiplexing (WDM), to an optical packet router using multiple wavelength labels, and to an optical packet network that uses multiple wavelength labels.
2. Description of the Prior Art
In the area of optical packet communications using optical fibers, photonic networks have been proposed in which not only trunk line links, but even switching functions in network nodes connecting a plurality of trunk lines, are implemented in the optical domain. In such a network, when each of the optical packets passes through a network node, it can autonomously switch to a predetermined route based on address information carried by the packet. In this respect, there is a need for an optical packet routing system that optically labels each packet with the respective address, checks and identifies the labels in the optical domain and, based on the identification result, switches the output route of the packet.
In prior art photonic networks based on the WDM technology, many configurations and methods have been proposed in which the routing labels are comprised as single wavelength optical signals. To identify the packet labels, this technology uses simple wavelength identification devices such as arrayed waveguide gratings (AWG), which are limited with respect to the number of labels that can be identified. Specifically, when single wavelength labels are used, with the existing level of technology, most networks can only handle around 100 to 200 labels, and the upper limit for any network is around 1000.
For the processing involved, there has been proposed a label switching router employing a phase code processor that uses an optical code division multiplexing (OCDM) system (K. Kitayama and N. Wada, “Photonic IP Routing,” IEEE Photon. Technol. Lett., vol. 11, no. 12, pp. 1689-1691, December 1999). In that system, the labels used are phase labels having a pattern comprised of a light phase, such as 0, π, for example, so that the labels are, for example, “000π”, “00ππ”, “0π0π,” and so forth, which are processed by a phase code processor. An input signal constituting a phase label is split into a plurality of signals, each of which falls incident on an independent optical correlation processor. Each of these optical correlation processors is configured to match, i.e. identify, a corresponding independent phase label. This differs from the present invention in terms of label configuration method and label processor.
With respect to optical encoding using time spreading/wavelength hopping codes, Japanese Patent No. 3038378 discloses a method in which streams of optical pulses having different wavelengths on a bit-by-bit basis are used for encoding by setting different codes within a code sequence specified for each channel, with decoding of received signals being effected by matched filtering in the time domain. This disclosure differs from the present invention in that the disclosure does not pertain to routing.
As described above, with respect to prior art optical packet routing methods and apparatuses, and optical packet network configurations, with current technology, when single wavelength labels are used, most networks can only handle around 100 to 200 labels, and the upper limit for any network is around 1000 labels.
An object of the present invention is to provide a method for routing optical packets using multiple wavelength labels, an optical packet router using multiple wavelength labels and an optical packet network that uses multiple wavelength labels, that enable wavelength resources to be effectively utilized by using wavelength division multiplexing to route optical packets with multiple wavelength labels, thereby greatly increasing the number of routing labels that can be used in a network compared to the number of routing labels that can be used in a prior art photonic network.
In a first aspect, the present invention achieves the above object by providing a method for routing optical packets using multiple wavelength labels, the method comprising: converting optical packet address signals to a plurality of optical pulses having different time-deviated wavelengths by executing a first operation to impart a wavelength dependent delay time with respect to a plurality of optical pulses having different wavelengths at a same time axis position and, when the optical pulses are transmitted along a predetermined optical path having dispersion, compensating for the dispersion by executing a second operation on the optical pulses corresponding to a reverse process of the operation to impart a wavelength dependent delay time, the second operation resulting in generation of a plurality of optical pulses having different wavelengths at a same time axis position, and using signals of the pulses thus generated to determine a transmission route.
In another aspect, the invention provides a method for routing optical packets using multiple wavelength labels, in which a predetermined waveband used for one-bit address signals and a one-bit data signal waveband have identical bandwidths.
In another aspect, the invention provides a method as described in which the bandwidth allocated to data signals included in optical packets is wider than the bandwidth allocated to address signals.
In another aspect, the invention provides a method as described in which address signals and data signals are transmitted with a predetermined time differential.
In another aspect, the invention provides a method as described in which optical packet address signals include address information that is identified by wavelength information delimited by a predetermined waveband width and predetermined time differential information.
In another aspect, the invention provides a method as described in which optical packet address signals include first address information that is identified by wavelength information delimited by a first waveband width, and second address information that is identified by wavelength information delimited by a second waveband width and predetermined time differential information.
In another aspect, the invention provides a method as described in which, based on first address information, routing is performed by a first router that can switch optical paths according to wavelength differences and, based on second address information, routing is performed by a second router that can switch optical paths according to time differences.
In a second aspect, the invention provides an optical packet router using multiple wavelength labels, the router comprising: mean for separating data signals and address signals identified by wavelength information delimited by a predetermined waveband width and predetermined time differential information included in optical packets; means for demodulating address information identified by the wavelength information delimited by a predetermined waveband width and predetermined time differential information from the address signals; means for switching an optical switch in accordance with demodulated address information; and selection means that uses the optical switch to select an optical route for the data signals.
In another aspect, the invention provides a router as described in which the demodulation means uses a multi-section fiber Bragg grating.
The invention also provides an optical packet router using multiple wavelength labels comprising: a pulse light source that includes multi-wavelength laser light; means for dividing pulse signals from the pulse light source into a plurality of light paths; a means for obtaining a first pulse signal using a means that interacts with a multi-section fiber Bragg grating following modulation of one divided pulse signal; a means for obtaining a second pulse signal comprising means for narrowing waveband width of other divided pulse signals and means for modulating the reduced-bandwidth pulse signals; means for adjusting a time differential between the fist pulse signal and the second pulse signal; and means for guiding the first and second pulse signals thus adjusted to a same light path.
In a third aspect, the invention provides an optical packet communication network that uses multiple wavelength labels, the network including a plurality of routers that can switch optical paths in accordance with differences in combinations of multiple optical pulse wavelengths and time differentials included in address signals, with at least two of the routers being connected together.
In another aspect, the invention provides an optical packet communication network that uses multiple wavelength labels, the network including a first router that can switch optical paths in accordance with differences in wavelengths of multiple optical pulses included in address signals, and a second router that can switch optical paths in accordance with differences in combinations of multiple optical pulse wavelengths and time differentials included in address signals, with the second router being connected to the first router.
Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and following detailed description of the invention.